Chrysanthemums, commonly known as mums, are the quintessential flower of autumn, providing a final burst of color as the gardening year winds down. These vibrant blooms are popular for seasonal outdoor decorating, often purchased in full flower for instant impact. Ensuring their lasting beauty and potential return requires specific care tailored to cooling temperatures and changing light conditions. Maintenance shifts dramatically from nurturing the flowers during their display to preparing the plant for winter.
Essential Care While Mums Are Blooming
For the longest display, mums require consistent attention while actively flowering in the fall. They thrive in full sunlight, needing a minimum of six hours of direct sun daily to maintain dense growth and maximize bloom production. Placing them in a sunny spot ensures the flowers develop intense, vibrant colors.
Proper watering is important, especially for container mums, which dry out quickly in fall winds. Keep the soil consistently moist but never waterlogged, as soggy conditions lead to root rot and fungal diseases. Watering at the base of the plant, rather than overhead, keeps the foliage dry and minimizes mildew risk.
To encourage new flowers, perform deadheading by carefully removing spent, faded, or browning blooms. Eliminating old flower heads redirects the plant’s energy away from seed production and toward developing new buds, prolonging the flowering period.
Pruning and Preparing for Dormancy
Once the fall display has ended, typically after a hard frost causes the foliage to brown and wilt, the plant transitions into dormancy. This is the time to cut back the plant’s structure in preparation for winter. Pruning helps the plant focus its remaining energy on strengthening its root system rather than sustaining dead top growth.
Use clean, sharp shears to cut the stems down to about four to six inches above the soil line. Leaving this short stem material helps gardeners locate the plant’s crown for later winter protection. Removing the bulk of the dead foliage also eliminates potential hiding spots for pests and reduces the chance of disease overwintering.
Some gardeners in colder regions may choose to leave the cut material in place until early spring. The remaining stems can offer a small degree of natural insulation by trapping leaves and snow around the plant’s crown. However, cutting back the plant remains the best practice for promoting overall health and preparing the garden for protective winter mulch.
Steps for Successful Overwintering
Successful overwintering of chrysanthemums depends on distinguishing between hardy garden mums and tender florist mums. Hardy garden mums, intended for perennial performance, have a better chance of surviving winter in the ground, typically in USDA Zones 5 through 9. Florist mums, generally sold for seasonal display, are not bred for cold tolerance and often have insufficient root systems to withstand deep freezes.
For hardy mums planted in the ground, preventing the soil from repeatedly freezing and thawing is key to survival. This causes “heaving,” which pushes the plant’s roots out of the soil. Plant them in well-draining soil in a sunny location as early in the fall as possible to allow for root establishment.
A crucial step is to apply a thick layer of protective mulch, such as straw, shredded leaves, or evergreen boughs, but only after the ground has frozen solid. The mulch layer should be three to four inches deep and spread over the plant’s crown and surrounding soil to insulate the roots and keep the soil temperature consistently cold. This insulation prevents the damaging freeze-thaw cycles that can kill the plant.
If you purchased a mum in a pot late in the season, move the entire container to a protected, unheated space, such as a cool garage or shed. Potted mums overwintered indoors should be kept in a dark or dimly lit area where the temperature remains consistently above freezing but below 50 degrees Fahrenheit. The plant is dormant and does not require light, but it must not be allowed to dry out completely. Check the soil every few weeks and provide a small amount of water if the top few inches feel dry, ensuring the plant’s roots remain viable until spring.